Air operated shears



Jan. 3, 1950 G.-POTSTADA AIR OPERATED SHEARS Filed Dec. 29, 1945 I I N V EN TOR. 650265 P0 75 77404 ATIUPNA-YS Patented Jan. 3, 1 950 George Potstada. Oakland, Calif.; Magdalena Potstadagadministratrix of said George Potstada, deceased ApplicationDecember 29, 1945. Serial No. 638,242

particularly pertains to such devices of the gen eral character illustrated, described and claimed in -my-co-pendingapplication entitled Pruning shears, filed January 4, 1945, Serial Number 571,325, now abandoned. It is the principal object of my present inven tion to generally improve the construction and operation of pruning shears of the character referred to whereby to provide pruning shears which will efiiciently operate to shear tree limbs and branches of diameters which could not be sheared by prior pruning shears but required the use oi pruning saws. v

In'practicing my invention I provide an elongated tubular member having a fixed blade secured at one end. A pivotal blade is pivoted to the fixed blade for shearing cooperation therewith. A connector rod extends through the tubular member and is connected at one end to the movable blade and at the other end to the piston of a pneumatic'motor so that operation of the piston will be "accompanied by operation of the shearing blade. The formation of the blades and the pivotalarrangement is such that a draw cutting action results, this plus the disposition. of the points of connection between those parts resulting in considerable leverage enables great easeof operation in shearing limbs and branches of a diameter which hitherto required sawing.

One form which the invention may assume is exemplified in the following description and illustrated by way of example in the accompanying drawings, in which:

Fig. l is a view in side elevation of my improved pruning shears with parts shown in central longitudinal section to disclose certain details or construction.

Fig. 2 is a transverse sectional view taken on line 2-2 of Fig. 1. v a

Fig. 3 is a vertical sectional view taken on line 33 of Fig.1.

' Referring more particularly to theaccompanying drawings, l indicates tree pruning shears embodyin my invention. These shears comprise an elongated rigid tubular member II which may be of any desired length, depending upon the length it is wished to construct the shears. Shears constructed in accordance with my invention would ordinarily be considerable in length in that its principal use is that of pruning fruit and other trees.

At-one end of the tubular member there is fixed thereon a fixed blade 12. This blade is constructed or two complementary members M which 2 Claims. (01. sip-zeal are identical-information except that they are right and left. At the longitudinal center of the members l4 they are formed with a socket l5 to receive the end of the tubular member H secured by welding or otherwise. As shown, the upper end of the tubular member I I is projectedinto the socket l5 andsecured therein.

At oneside of the tubular member a filler member I6 is inserted between thetwo members M of the fixed blade i2 so that the working edge ll of the fixed blade will have a shallow recess formedtherebetween for the reception of the cutting-edge l8 of a pivotal or movable blade 19.

From Fig. -1 it will beseen that theworking edge ll of the-fixed blade is concave in that it starts from its outermost point, and extends inwardly and laterally, and then on a radius back to the longitudinal center of the tubular member. To this. extent the working face I! of the fixed blade is rather hooked in shape but is definitely concave so. that it may receive and hold the branch or limb to be cut in cutting position. The filler member'lii. extends short .of the working edge I! so that. the cutting edge It of the pivotal blade l9 may penetrate into the recess formed intermediate the side faces of the working face or edge I! and insure complete severance.

The movable or pivotal blade 19 is interposed between the members l4 and is pivoted to the fixed'bladeas at 20. ,Itwill be noticed that the pivotal point 20 is disposed at a distance to the side of thefixed blade l2 and the axial center of the tubular member II opposite the side in whichis formed the working edge ll of the fixed blade l2.

The. cutting edgev N3 of the movable blade I9 is convex or curvilinear, as illustrated, and at its extremity; or the point indicatedat 2!, it has a stop member to engage the extremity 22 of the fixed'blade 12 so as to'prevent the edge of the movable blade from being abutted against the fixed blade with excess pressure.

' The disposition of thepivotal point 20 relative to the cutting edge 18 of the movable blade 19 and the working edge 11 of the fixed blade I2 issuch, that the cutting edge I8 will move transversely relative to the-working face l1, while at the same time moving longitudinally thereof so as to produce a drawing or slicing type of action. Thus, there is obtained a clean shearing ofthe branch or limb to be out without any tendency to crushthe same. Likewise, this enables a cut to be made with less 'eiTort than would be required by astraight shearin action.

Mounted concentrically within the tube II is adjacent surface of; piston 29;

rigidly fixed on the pneumatic cylinder 26 sh that the latter will be fixedly mounted at-the" end of the tube II. I may prefer to connecflthe' gland 25 to the tube II byxmea'risaofia union 28* to enable disconnection of tiiepneuma'tici'rcylih der 26 therefrom, if I so desire.

Rigidly mounted in the cylinderJfi-and-snuggly fitting the bore thereof is a'pistbnifwhich is fixed concentrically at the end of the connector 1 rod 23 which extends tliiough the gland 25. At the endjofi the cylinder: 2-6- l osite thehead. 2! is ansecond cylinder head 30::formedwith a-socket 3-:| receiving-one end-of a compressionspring 32; The other end of this=spring bears against the constantly tends to :maintain the piston 29 in-its uppermost position whichdisposes thecutting or shearing blade ;I 9 to-its'open 901' normal position.

Formediin the-.baseofthesocket32in the cylin der. head30 isa threaded opening to receive the complementalq threaded section of: a: piston stop in the sprin'g, 3 2- and :in axial alignment with the axisof thepistori Z 9: "I hereoiprocable movement of the piston29-isathereby-limited by the cylinder head' i2-l an'dthestop-32ai' Byturning the stop 32a in the cylinder headr30;.itcanine-adjusted upwardly or downwardly relative thereto, and the length'of. the stroke of. the p'iston 29' varied as is desired; 7 A look nut 32hhas been' pnovidedto hold rotary control- :valves; 33shaving aan intake port 34 and' an exhaust port 35. The intake =1: ort-I34: 'is v adapted to form a: communication between a source 1 of air under? pressure conducted: Zto a port 7 a 35 by means of a suitable connection 31 rand'ia cylinden'intakeaport 38 formed'sthroughlthehea-d 2.1 ofztheicylinderx V When the valve::33: is turned to register the intake port. 34: with the; intake port 38 of. the" cylinder head 2 1; air 'underz'pressureu from" Icon nection 3'Iim ay passathrough theJport SB; the port" 34 in the rotary'controlavalve 33jzth'e' intake'iporti 381: into *the cylinder? air one: endi'o'f: the; piston forcing the: latter; toward thei-heads3n This Will axially move ithe connector rod-23 to actuate the cutting blade I 9 causi'n'g: the" latter to effect a shearingi cut as previously described; When" the valve '33- is turned-J to place. th'efup'ort 34": out of register. with. the port 3851 the exhaust 'port 35 automatically! registers an: exhaust" port" 3511- in the'valve'casing and an exhaust-port 35b in the cylinder head so thatitheiiendioftlie cyliiider a'djacentnthe; head-2 1will; cation 1 withthe atmosphere:

The spring- 32 H 4 move the cutting blade l9 to open or normal posi tion. The piston 29 will be moved to accomplish such result by the spring 32.

The rotary valve 33 is provided with an operating handle 39 to enable the operator to actuate the shearing head of the shears through the medium of the pneumatic motor, as previously described.

For orchard work. I intend that a= portable source 'ofrair under pressure be provided and that the same 'be connected by a flexible hose or other connection- 3'! to the pneumatic motor so that the operator may freely Work beneath the trees in".- prunin the= same:

The entire device is of light-- weight so th'at an operator may easily manipulatethe: same.

Inc-actual, practice I construct the pruning shears substantiallya's illustrated and described V 32a whi'ch extends upwardly concentricall withwith the length of the tubular member ll calculated to meet the conditions to which the pruning shears are-to-be ut, Due L to I the; provision: of thei sprin 3Z=the movable blade lit-will be normallywdisposediin open position; so that the hooked or concave working faceofathe stationary bladesmaybeqhooked on to.-the-branch or limb, to be sheared and disposethelimbinthe curved portion of the workingface 11 se thatgthe full force 7 andeffect-0fv the cutting; action will be applied when the blade: l9-is actu-ated to effect-the. shear. In that the blade-- I9 is constr-ucted andso mounted that thecutting action will beta drawing or' slicing out but a minimum -ot .power, is necessary to effect theesevering of: the branch on limb.

Tooperate the blade l 9 to effect the: shearing, the operator turns the handle 3-9 so thatther-port 34 or, the valve33=registers-with the cylinder: port; 38. Thisforces' the piston 29; toWard' the head- 30rof the-cylinder '26. -This movement of the piston 29 efiectsV-axial -movement of. the connector: rod23; causing the blade l9 to-pivot'aboutitspivotpoint and perform=its:shearing Qperationin conjunction-with the stationary Workingface, as"- previously-describedx After the; out or severance: has! been effected; the operator againmanipulates I the:h'andle 3-9 etc,

1 place: the port 34 iout .of register with r the cylin placed in communi- V permitthe iston' 2-9 to move axially-1towarttithe'iieadifliandfthereby' .25;

der port 38 and place the exhaust port 35 in rege ister; with the exhaust ports -35a aand 35b) allow-- ing the air; under pressure inither cylinder: to ex haustto the-atmosphere; 'As this airis-exhausted, the spring32' will move the; piston-29 tOWBXdgthe; piston head :23; again plabingtheblade l Sl -through the medium of the connector rod 23 in open posi=- tion f or'a subsequent-operation: To prevent air compression in thGGIldaO-f theIcyli-nder adjacent: the head 30,1b188d61 ports 34la-areprovidedin the head member 30.

It=should bernotedithat the piston stop 3211; can be so adjusted that piston 29 WiILmOVQ -WithiHY the cylinderr26vonly suchdistanceas is necessary to effect the shearing operation. This relievesf thev connector rod 23; ,the movablel blade: I Stand their"pivotalconnection of .further stress or: ten-a sion-after the shearin g operationhas'been cQm piloted. While,zas statedabove, tthesstopamember; at .2 l 'preventsthe edge of the movable blade from abutting again'st'th'e fixed blade with exce'ssa'pres' sure, It prefer to adjust the piston: stop"- so. that the pivotal movement :of the movable blad will terminate: immediatelybeforefthe' stop member at 2| strikes the extremity 22 on the fixed blade;

Thus the? forcing offth movable blade against the uny'ielding fixed blade can he prevented;

From the foregoing? it is obvious 'that rhave provided an improved pruning shears capable of use in pruning the comparatively large branches or limbs of trees. To my knowledge there have been no prior shears capable of shearing such large branches or limbs and that it has been the practice hitherto to prune the branches or limbs by making use of a pruning saw.

Obviously by the use of my improved pruning shears, an operator may by the use of a single tool not only prune the smaller branches and stems but may at the same time and with the same tool shear the larger limbs which hitherto required the use of a pruning saw.

While I have shown the preferred form of my invention, it is to be understood that various changes may be made in its construction by those skilled in the art without departing from the spirit of the invention as defined in the appended claims.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. Pruning shears comprising a tubular member, a fixed blade rigidly secured on one end of said tubular member and having a working face at one side of the longitudinal center of the tubular member beyond the end thereof, a movable blade pivoted to the fixed blade and having a working surface disposed on the opposite side of the center of the tubular member when said blade is in open position, a pneumatic motor having a cylinder with two opposing cylinder heads, the first of said cylinder heads being secured to and in axial alignment with said tubular member, a movable piston in said cylinder, an elongated connector rod extending through said tubular member and connected at one end to the movable blade and at the opposite end to said piston whereby reciprocation of the latter will correspondingly actuate the former, a stop member adjustably mounted in the second of said cylinder heads to limit the reciprocable movement of the piston,

a compression spring disclosed intermediate said second cylinder head and piston tending to move said piston toward the first cylinder head, and manually operated valve means to be connected with a source of air under pressure and operable to admit the same to the cylinder to actuate the piston and move it toward the second cylinder head.

2. A pneumatic motor comprising a cylinder having two opposing cylinder heads, the first of said cylinder heads being adapted to be mounted on the end of a tube in such a manner that the cylinder is in axial alignment with said tube, a movable piston in the cylinder, a coil spring disposed intermediate the piston and the second cylinder head constantly urging the piston toward the first cylinder head, manually operated valve means to be connected with a source of air under pressure and operable to admit the same to the cylinder to actuate the piston and move it toward the second cylinder head, and a stop member adjustably mounted in said second cylinder head whereby the stroke of the piston can be limited to a predetermined length.

GEORGE POTSTADA.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 146,439 Ellis Jan. 13, 1874 728,068 Young May 12, 1903 2,075,341 Goodman Mar. 30, 1937 2,366,909 Johnson Jan. 9, 1945 FOREIGN PATENTS Number Country Date 557,609 France May 8, 1923 

